[Filter Test] AndreaU MK-I, BaaderU, Hoya U360 Stack, StraightEdgeU (v2016) and The Standards

[Andrea B.]

No filter testing would be complete without seeing it used to photograph white standards and the CC Passport. :D

 

You can read all the details about the test in the next post.

 

The quick summary is this: For f/8 @ ISO-100, the AndreaU Mk-I was slightly faster than the other UV-pass filters and the U360(2.00)+S8612(1.75nn) was slightly slower. The StraightEdgeU and the BaaderU were between those two, having approximately the same shutter speeds.

 

Another observation is that the StraightEdgeU and the AndreaU Mk-1, although different types of filters, both capture more near-400 UV than the BaaderU or U360+S8612 stack. Thus, their raw captures record more in the Blue channel than do captures made with the BaaderU or a U360 stack.

 

The results from Data Set 3 are shown here.

White balance was made on the white standards. (....where else?? )

For the visible photo, focus was made on the standards so that the CC Passport itself would be slightly soft and thus provide "smoother" colour blocks as recommended for creating a colour profile in Photo Ninja. I did not reset focus for the UV photos.

 

Note: I can see that the conversion to sRGB JPG and online display has cause some colour casts on the white standards not visible when working with the raws/tiffs.

 

Visible

^{Remember, this is OOF on purpose!}

[iso100]_20160822_13243830wf_49384pn.jpg]

 

StraightEdgeU

[iso100]_20160822_13271010wf_49424pn.jpg]

 

AndreaU

[iso100]_20160822_13252060wf_49397pn.jpg]

 

BaaderU

[iso100]_20160822_13260060wf_49408pn.jpg]

 

U360+S8612

[iso100]_20160822_13293210wf_49442pn.jpg]

 

 

Here are the raw composites of those standards shots so you can see the purple/blue tones in the StraightEdgeU and AndreaU files and the red/orange tones in the BaaderU and U360 files.

 

StraightEdgeU

[iso100]_20160822_13271010wf_49424rawComp.jpg]

 

AndreaU

[iso100]_20160822_13252060wf_49397rawComp.jpg]

 

BaaderU

[iso100]_20160822_13260060wf_49408rawComp.jpg]

 

U360+S8612

[iso100]_20160822_13293210wf_49442rawComp.jpg]

[Andrea B.]

Test 1: Compare Four UV-Pass Filters on Standards

Date: 22 August 2016

By: Andrea G Blum, UltravioletPhotography.com, Middletown, NJ, USA

Location: Middletown, NJ

 

Filters: Baader UV/IR-Cut Visible-Pass Filter

Baader Planetarium 48mm BaaderU UV-Pass Filter on 48-52mm StepRing

UVIROPTICS 52mm Schott glass U360(2.0mm)+S8612(1.75mm) UV-Pass Filter Stack

UVR Optics 52mm AndreaU-MkI UV-Pass Filter

UVR Optics 52mm StraightEdgeU UV-Pass Filter

 

Gear: Nikon D600-Broadband + Coastal Optics 60/4.0 + RRS Groundpod

 

Subjects:

• Labsphere 99, 75 and 50% Reflective Spectralon Standards
  
• Xrite Color Checker Passport
  

Conditions: Sunny and hot with rapidly passing fair-weather cumulus. Occasional mild breeze.

Solartech Solarmeter 5.0: 4.8 - 5.0 mW/cm2 (for UVA/UVB between 280-400 nm).

The sun was behind the photographer and camera directly illuminating the subjects. Photographs were made only when the sky was clear and sunlight was at the strength given.

 

Exposure: f/8 @ ISO-100 with varying speeds as needed.

 

Other:

LiveView: Viewable meter needed because the viewfinder must be closed for UV work.

Picture Control: Monochrome, for exposures of maximum luminosity without misleading false colour.

ADL: Low, for a slight dynamic range boost without affecting shutter speed.

Metering: Matrix

Mode: Manual

 

Converter: Photo Ninja 1.3.4b

For all UV photos in this test, the conversion steps were: demosaic, apply gamma correction, autoscale histogram, set white balance on Labsphere 99% reflective (center white) standard and apply Plain colour control with saturation 65. For the sake of uniformity, Photo Ninja's Daylight/Flash Light Source was used for color profiling. No exposure adjustments were made. No sharpening was added.

For the Visible reference photos, the only change to the preceding conversion was to apply a D600 colour profile in place of Photo Ninja'sDaylight/Flash Light Source.

 

Test Procedure: Photograph standards for later colour profiling and for comparisons.

Focus was made on the Labsphere standards so that the Color Checker Passport would be slightly out-of-focus as needed for a proper color profile made later in Photo Ninja. Re-focus was performed with each filter change. Additional test procedues are described in the following Data Set summaries.

One drawback of this test is that typically only blue or blue-violet false color tones are seen.

 

Data Set 1: Data was taken between 13.13.03.50 to 13.15.37.40 for 2 min 33.9 secs.

A photo was made for each filter at the metered speed for f/8 @ ISO-100 with the focus square on the Labsphere 99% white disc. As a result, for all four UV-pass filters, the photos were underexposed. This is not unexpected because camera meters typically underexpose 99% white reflectivity, and the white disc remains very reflective in UV.

 

Data Set 2: Data was recorded between 13.17.52.40 to 13.23.14.80 for 5 min 22.4 secs.

An initial photo was made for each filter at the metered speed for f/8 @ ISO-100 with the focus square on the Labsphere 99% white disc. Then that exposure was pushed to the right in 1/3-stop increments. From each series exposures having similar luminosity histograms were chosen for conversion and analysis. The only alteration during the conversion described above was the use of the Labsphere 75% or 50% reflective standard for white-balancing when the 99% standard was blown (and thus unusable) due to a pushed exposure.

 

Data Set 3: Data was recorded between 13.23.47.60 to 13.29.42.00 for 5 min 54.4 secs.

The procedure for Data Set 3 was identical to that of Data Set 2.

 

Shutter Speed Summary for f/8 @ ISO-100:

Data Set 1: Shutter speeds as metered.

Visible 1/640"

AndreaU MK-I 1/8"

BaaderU 1/4"

StraightEdgeU 1/5"

U360 (2.00mm) + S8612 (1.75mm) 1/3"

 

Data Set 2: Shutter speeds optimized.

Visible 1/640"

AndreaU MK-I 1/4"

BaaderU 1/2"

StraightEdgeU 1/2"

U360 (2.00mm) + S8612 (1.75mm) 1/1.3"

 

Data Set 3: Shutter speeds optimized.

Visible 1/500"

AndreaU MK-I 1/3"

BaaderU 1/1.6"

StraightEdgeU 1/2"

U360 (2.00mm) + S8612 (1.75mm) 1/1.3"

 

Conclusions from the Data:

The AndreaU Mk I was consistently the fastest filter. However, the photo histograms indicated that the AU photos were also consistently underexposed for reasons I'm not sure of, but attributable no doubt to my error. I would estimate that the AU exposures should have been increased by 1/3 stop. The U360 (2.00mm) + S8612 (1.75mm) filter stack was consistently the slowest filter, but this is not unexpected given the total thickness of the stack at 3.75mm. The BaaderU and the StraightEdgeU had very similar speeds with the StraightEdgeU faster by 1/3 stop in two cases.

 

Subjective Impression 1:

Photos made with the AndreaU MkI or the StraightEdgeU have a similar appearance. Similarly, photos made with the BaaderU or the U360+S8612 stack also have a similar appearance. Data Set 3 was arbitrarily chosen for conversion in Raw Digger 1.2.6 (Build 447) to illustrate these similarities by presenting the raw composite which shows the raw colours before white balance. Subsequent conversion to a JPG sRGB profile may have slightly altered the raw colour appearance but not so much as to make this impression invalid.